This figure of a woman, dressed in the Florentine fashion of her day and seated in a visionary, mountainous landscape, is a remarkable instance of Leonardo's sfumato technique of soft, heavily shaded modeling. The Mona Lisa's enigmatic expression, which seems both alluring and aloof, has given the portrait universal fame.

The above paragraphs are from the La Joconde essay on Mona Lisa. You can read the full essay at WebMuseum.

It seems I'm not the first artist to be inspired by this painting. Here's a couple of sites that are completely devoted to La Gioconda: